JPH0684102B2 - Thermal recording material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a high-sensitivity heat-sensitive recording material having excellent thermal response.

(B) Prior Art A heat-sensitive recording material generally comprises a support and a heat-sensitive recording layer mainly composed of an electron-donating, usually colorless or light-colored dye precursor and an electron-accepting developer. By heating with a head, a heating pen, a laser beam, etc., the dye precursor and the developer react instantaneously to obtain a recorded image, which is disclosed in JP-B-43-4160 and JP-B-45-14039. Has been done. Such a thermal recording material has the advantages that it can be recorded with a relatively simple device, is easy to maintain, and does not generate noise. It is a terminal for measuring recorders, facsimiles, printers, and computer terminals. It is used in a wide range of fields such as automatic ticket vending machines such as labels and tickets. In particular, in the case of facsimiles, the demand for the heat-sensitive system has greatly increased, and at the same time, the speed is being increased to reduce the transmission cost. Corresponding to the speeding up of such a facsimile, there has been a demand for higher sensitivity of the thermal recording material.

Accelerated fax is standard A4 originals from a few seconds to 20
Since the data is transmitted and received in seconds, the current flowing through the facsimile thermal head is repeated for a very short time of less than a few milliseconds, and the thermal energy generated thereby is transmitted to the thermal recording sheet to carry out the image forming reaction. .

In order to carry out the image forming reaction with the heat energy transferred in such a short time, it is necessary that the heat sensitive recording material has excellent thermal responsiveness. In order to increase the thermal reactivity, the compatibility between the color developing agent and the dye precursor must be improved. A sensitizer is used for this if necessary. When the sensitizer melts itself by the transferred heat energy, the sensitizer has a function of dissolving or encapsulating a dye precursor and a developer in the vicinity to accelerate the color-forming reaction. Alternatively, improving the compatibility with the dye precursor and the color developer is one method for increasing the sensitivity of the heat-sensitive recording material.

As such a method, waxes are disclosed in JP-A-48-19231, JP-A-49-34842, JP-A-50-149353, JP-A-52-106746, and JP-A-53-5636. JP-A-57-64593 and JP-A-58-87094 disclose naphthol derivatives, JP-A-57-64593 and JP-A-57-64593.
-64592, JP-A-57-185187, JP-A-57-191089, and JP-A-58-110289 disclose naphthoic acid derivatives,
7-148688, JP-A-57-182483, JP-A-58-112788,
JP-A-58-162379 discloses that a benzoic acid ester derivative is added.

However, the thermal recording materials produced by using these methods are still insufficient in terms of color density and color sensitivity.

(C) Purpose of the Invention The present inventors have investigated various sensitizers for the purpose of obtaining a highly sensitive heat-sensitive recording material having further excellent thermal response.

(D) Structure of the Invention In a heat-sensitive recording material containing a color developing agent which reacts with a normally colorless or light-colored dye precursor upon heating to develop the dye precursor, a compound represented by the following general formula is used as a sensitizer. By incorporating it, a high-sensitivity heat-sensitive recording material excellent in thermal response could be obtained.

General formula (However, R represents halogen, a lower alkoxy group, a lower alkyl group. N represents an integer of 0 or more and 3 or less.) Specific examples of the compound represented by the above general formula include those shown below. .

The compound of the above general formula can be easily obtained by a known method.

The sensitizer according to the present invention is usually added in an amount of 5% by weight or more based on the color developer. A preferred amount is 10 to 400% by weight, especially 2
0 to 300% by weight is preferred. If the addition amount is less than 5% by weight, the sensitivity improving effect is not sufficient, and if the addition amount is more than 400% by weight, it may be economically disadvantageous.

The main components used in the heat-sensitive recording material of the present invention will be specifically described below, but the present invention is not limited thereto.

Examples of the dye precursor include triphenylmethane-based, fluorane-based, diphenylmethane-based, thiazine-based and spiropyran-based compounds. For example, 3,3-bis (P-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindole-3 −
Yl) -4-azaphthalide, 3-diethylamino-6-
Methyl-7-chlorofluorane, 3-diethylamino-
7-chlorofluorane, 3- (N-cyclohexylamino) -7-methylfluorane, 3-diethylamino-7
-Methylfluorane, 3-diethylamino-6-chloro-7-methylfluorane, 3-diethylamino-7-anilinofluorane, 3-diethylamino-6-methyl-
7-dibenzylaminofluorane, 3- (N-ethyl-
Np-toluidino) -7-anilinofluorane, 3-
Diethylamino-7- (O-chloroanilino) fluorane, 3-dibutylamino-7- (O-chloroanilino)
Fluoran, 3-diethylamino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-p-toluidino) -6-methyl-7-aninolifluorane, 3-
(N-methyl-N-cyclohexylamino) -6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-
Methyl-7-anilinofluorane, 3-diethylamino-7- (m-trifluoromethylanilino) fluorane, 3- (N-ethyl-N-isopentylamino) -6
-Methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (p-phenetidino) fluorane, 3-dibutylamino-7- (O-fluoroanilino) fluorane, and the like.

As the developer, an acidic substance generally used for thermal paper,
That is, an electron-accepting compound is used, and particularly a phenol derivative or an aromatic carboxylic acid derivative is used. Among the phenol derivatives, preferred compounds are at least 1
It is a compound having one or more phenolic hydroxyl groups, and more preferably an ortho-position of the phenolic hydroxyl group is an unsubstituted phenol derivative. For example, phenol, pt-butylphenol, p-phenylphenol, 1-naphthol, 2-naphthol, p-hydroxyacetophenone, 2,2'-dihydroxybiphenyl, 4,4'-isopurpyridenediphenol, 4,4 ′ -Isopropylidene diphenol, 4,4′-isopropylidene bis (2-t-butylphenol), 4,4′-isopropylidene bis (2-chlorophenol), 4,4′-cyclohexylidene diphenol, 2, 2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) pentane, 2,2-bis (4-hydroxyphenyl) hexane, diphenolacetic acid methyl ester, bis (4-hydroxyphenyl) Sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4'-methyldif Vinyl sulfonic, 4-hydroxy-4'-isopropyl sulfone, bis - (4-hydroxyphenyl) sulfide, 4,4'-
Thiobis (2-t-butyl-5-methyl) phenol,
7-bis (4-hydroxyphenylthio) -3,5-dioxyheptane, novolac type phenol resin, etc.,
As the aromatic carboxylic acid derivative, for example, benzoic acid,
p-t-butylbenzoic acid, p-hydroxybenzoic acid, p
-Hydroxybenzoic acid methyl ester, p-hydroxybenzoic acid isopropyl ester, p-hydroxybenzoic acid benzyl ester, gallic acid lauryl ester, gallic acid stearyl ester, salicylanilide, 5-chlorosalicylanilide, zinc 5-t-butylsalicylic acid And metal salts such as zinc hydroxynaphthoic acid. Further, a thiourea derivative may be used, and examples thereof include N, N'-bis (3-chlorophenyl) thiourea.

As the binder, starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, styrene-maleic anhydride copolymer, water-soluble binder such as ethylene-maleic anhydride copolymer, styrene Examples include latex-based water-soluble binders such as -butadiene copolymer, acrylonitrile-butadiene copolymer, and methyl acrylate-butadiene copolymer.

Examples of the pigment include diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide, and urea-formalin resin.

In addition, for the purpose of preventing head wear and sticking, higher fatty acid metal salts such as zinc stearate and calcium stearate, waxes such as paraffin, oxidized paraffin, polyethylene, oxidized polyethylene, stearic acid amide, and castor wax, Examples thereof include dispersants such as sodium dioctylsulfosuccinate, ultraviolet absorbers such as benzophenone-based and benzotriazole-based, and surfactants and fluorescent dyes.

Paper is mainly used as a support for the heat-sensitive recording material according to the present invention, but various non-woven fabrics, plastic films, synthetic papers, metal foils, etc., or a composite sheet in which these are combined can be optionally used.

(E) Synthetic Examples and Examples The present invention will be described in more detail with reference to synthetic examples and examples. However, the present invention is not limited to the following synthesis examples and examples.

Synthesis Example 1 Synthesis of compound (1) Parachlorophenol 10.1 g, 26.1% sodium hydroxide aqueous solution 13.4 g, cinnamyl bromide 12.2 g and acetone 10
Added to 0 ml. The system was heated and placed under reflux conditions for 8 hours and a half, and then toluene and water were added to separate the layers. The organic layer was washed with aqueous sodium hydroxide solution and dried over anhydrous potassium carbonate. The solvent was distilled off and the residue was treated with ethanol to obtain the desired product. This was recrystallized from ethanol to obtain 8.2 g of the desired product. mp = 90.5 to 92 ° C. Synthesis example 2 Synthesis of compound (2) Synthesis example 1 except that 9.7 g of paramethoxyphenol was used instead of 10.1 g of parachlorophenol used in synthesis example 1.
7.4 g of the target product was obtained in the same manner as described above. mp = 106.5 to 109 ° C. Example 1 20 g of 3-diethylamino-6-methyl-7-anilinofluorane was dispersed in a ball mill together with 80 g of a 1% polyvinyl alcohol aqueous solution. On the other hand, 50 g of 4,4 ′ isopropylidene phenol was dispersed by a ball mill together with 200 g of a 1% aqueous solution of polyvinyl alcohol, and 50 g of the compound (1) was similarly dispersed together with 200 g of a 1% aqueous solution of polyvinyl alcohol.

After mixing these three dispersions, add 40
% Dispersion 125 g, 25% zinc stearate dispersion 40 g, and 10.5% polyvinyl alcohol aqueous solution 285 g were added, and the mixture was sufficiently stirred to obtain a coating liquid. The coating liquid is applied to a base paper having a basis weight of 55 g / m ^{2 so} that the solid content is 6 g / m ² and dried,
A heat sensitive recording material was obtained by processing with a super calendar.

Example 2 A thermosensitive recording material was obtained in the same manner as in Example 1 except that 50 g of the compound (2) was used instead of 50 g of the compound (1) used in Example 1.

Comparative Example 1 A thermosensitive recording material was obtained in the same manner as in Example 1 except that 50 g of N-hydroxymethylstearic acid amide was used instead of 50 g of the compound (1) used in Example 1.

Comparative Example 2 A thermosensitive recording material was obtained in the same manner as in Example 1 except that the dispersion liquid of the compound (1) in Example 1 was omitted.

Evaluation The optical densities of the images obtained by printing on the thermal recording materials obtained in Examples 1 and 2 and Comparative Examples 1 and 2 using FACOM FAX-621C, a facsimile machine manufactured by FUJITSU LIMITED, are Macbeth RD-51.
It was measured using 4. The results are tabulated.

(F) Effect of the invention As shown in the table, the use of the sensitizer according to the present invention makes it possible to obtain a heat-sensitive recording material having excellent thermal response.

Claims (1)

[Claims] 1. A heat-sensitive recording material containing a color developing agent which reacts with a normally colorless to light-colored dye precursor upon heating to develop the dye precursor, characterized by containing a compound represented by the following general formula. Heat sensitive recording material General formula (However, R represents halogen, a lower alkoxy group, a lower alkyl group. N represents an integer of 0 or more and 3 or less.)